White Skins

The idea that early humans became fair-skinned as they migrated north out of Africa so they could make enough vitamin D to stay healthy has been questioned again, reopening a debate that many think is settled.

Juzeniene and her colleagues recently reviewed alternate hypotheses for why humans might have evolved lighter skin. One highly controversial idea involves sexual selection: once sensitive light skin was no longer hazardous, as in Africa, it was selected for sexual attractiveness.

The other idea is that dark skin was more prone to frostbite in higher latitudes, and hence would have come under negative selection pressure, a claim that comes from studies of soldiers during the Korean War, when black soldiers suffered far more frostbite than white soldiers